Investigation of novel methods to remove the cyanotoxin, Cylindrospermopsin, from drinking water.
Chandu, Vijith Cholakkal Parambil
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The widespread distribution of cyanobacteria and their toxic effects on humans has become a major concern for researchers. Cyanobacteria are a group of oxygenic phototrophic bacteria that exhibit an enormous diversity in shapes and arrangements and occupy widespread habitats that include brackish, marine and fresh water. The major concern among these organisms is not so much the cyanobacteria themselves but their toxin production. Under suitable circumstances, cyanobacteria can reach high biomass levels and form toxic algal blooms. These toxins, known as cyanotoxins, are produced as secondary metabolites by several cyanobacterial species. Cyanotoxins affect not only aquatic ecosystems but also impact on human health. The current work focuses on the cyanotoxin cylindrospermopsin that was originally known to be produced by the cyanobacterium species Cylindrospermopsis raciborskii but has since been identified in a number of other cyanobacterial species. Cylindrospermopsin is hepatotoxic and acts as a strong inhibitor of protein synthesis. The increasing occurrence of toxic cyanobacterial blooms is of major concern, particularly within drinking water supply systems. Therefore, the investigation of more effective water treatment technologies is of great importance in order to ensure the removal of these potent toxins. There are many techniques that have been used so far, but the need to use an effective and efficient method to remove the toxicity is paramount. Removal of the toxin by the use of microbial degradation has been evaluated. Experiments with different strains of bacterial isolates showed positive signs in the removal of toxin by Biolog MT2 assay. In addition to that shake flask culture experiments were carried out and did not show any significant removal of the toxin. Studies with natural water sources showed some pronounced effect on the removal of CYN. The use of TiO2 photocatalysis as another potential water treatment strategy was also evaluated. Current study successfully demonstrated the potential degradation of purified cylindrospermopsin using the titanium dioxide (TiO2) photocatalysis treatment method. TiO2 photocatalysis was performed by using a powder form (Degussa P25) catalyst effectively removing the toxin; however, the powder is difficult to remove from the treated water. TiO2 pellets (Hombikat K01/C) were found to be slower in degradation although they allowed for an easier adaption to a continuous treatment system. As an alternative Photospheres™ (buoyant glass beads coated in TiO2) was evaluated and showed the same efficacy as that of Degussa P 25. Studies were extended to investigate the application of UV-LEDs in the photocatalysis reaction to show better efficiency.